It is known from U.S. Pat. No. 5,497,609, for example, to produce a textile yarn by decomposing a bundle of fibers into individual fibers, i.e. singling the fibers, by means of a separating rotor or wheel, and then feeding the single fibers to a fiber collecting surface which is formed as a perforated trough. The perforations of the trough are connected with a suction source so that the individual fibers can be drawn into the trough. The result is a packet of parallel fibers which are consolidated by imparting a twist to them as they are drawn from the trough. As additional fibers accumulate at the end of a yarn as it is thus formed, a continuous spinning process is ensured for producing practically endless yarn.
The earlier system has been found to require the twisting of the fiber packet to enable it to be drawn from the trough. To produce the twist and to assist in drawing the yarn from the trough, counter travelling belts may be used and it has been found in practice that such systems are subject to a high degree of wear and can give rise to the variations in the twist and yarn withdrawal speeds because of difficulties in precisely establishing and controlling the belt speeds. It is also possible to provide the trough so that it feeds into the nip between two cooperating perforated rollers or drums which are driven in the same sense and which rotate about mutually parallel axes, or a system in which the trough is formed between two such perforated drums under suction.
When the fiber packet is moved over a stationary perforated surface or is displaced transversely to the fiber collecting surface and thus the fibers must be drawn over the perforations at which suction is maintained, there is a tendency for some of the fibers at least to be partially drawn into the perforations. Fibers which are trapped in such perforations can lose their parallelity and stretched out orientations, can be shifted in the yarn, can be bent into hairpin shape or can be given a corkscrew shape, all to the detriment of the yarn and the desired uniformity and reproducibility thereof.